1. Technical Field
The present invention relates to a magnetic bearing device, a rotating mechanism, and a model identification method of a magnetic bearing main unit or a rotating machinery main unit. More particularly, the present invention relates to the magnetic bearing device for transmitting a signal between the magnetic bearing main unit and a control device by a power line communication with an alternating-current coupling. In addition, the present invention relates to the model identification method of the magnetic bearing main unit of the magnetic bearing device or the rotating machinery main unit of the rotating mechanism of a constitution in which the control device (the control device set with a control condition optimal for each model) having a different control condition according to each model is connected via a dedicated cable with the magnetic bearing main unit or the rotating machinery main unit for supporting a rotating body by a bearing.
2. Related Art
A magnetic bearing control system has a large-scale structure as a whole in which a magnetic bearing main unit including an actuator and connected with a turbo-molecular pump and the like and a control device constituted with a displacement detection sensor, a signal processing circuit, a compensating circuit, a motor drive circuit, and so forth are integrated. As it causes a restriction of an installation location and a deterioration of a maintenance performance, the magnetic bearing main unit and the control device are generally disposed in separate places and connected by a dedicated cable in a constitution.
FIG. 25 shows a block diagram of a conventional magnetic bearing device 100X. In FIG. 25, the magnetic bearing control device 100X includes a magnetic bearing main unit 10X, a control device 20X, and a dedicated cable 30X for the connection. The magnetic bearing main unit 10X has an electromagnet 51 for magnetic bearing as well as a positional displacement detection sensor 52 and a signal processing circuit 53. The electromagnet 51 for magnetic bearing supports a rotational shaft by a magnetic levitation for example, with a magnetism between two couples of radial electromagnets facing about the rotational shaft (11R in FIG. 1) of a magnetic rotating body (11 in FIG. 1) and a magnetism between a couple of axial electromagnets and controls the position of the rotational shaft by the balance of the magnetisms between the electromagnets. The positional displacement detection sensor 52 detects the positional displacement of the rotational shaft. The signal processing circuit 53 outputs the detected positional displacement signal as a signal at an appropriate level to a compensating circuit 54 in a next step. The output of the signal processing circuit 53 is transmitted to the compensating circuit 54 of the control device 20X via a signal wire in the dedicated cable 30X. The control device 20X has the compensating circuit 54, a bearing drive power amplifier 55, and a circuit drive power supply 56. The bearing drive power amplifier 55 generates a magnetism for magnetically levitating and for rotatably supporting the magnetic rotating body in the electromagnets constituting two radial magnetic bearings and the electromagnet constituting one axial magnetic bearing. In addition, the bearing drive power amplifier 55 supplies a direct current for adjusting the displacement of the magnetic rotating body by balancing the magnetisms in the electromagnets. The compensating circuit 54 supplies to the bearing drive power amplifier 55 with the compensating current to each electromagnet for constituting magnetic bearing corresponding to the amount of the positional displacement. The circuit drive power supply 56 supplies an electric power to necessary components constituting the magnetic bearing device 10X such as the electromagnets, a motor, a sensor, and an electric circuit. The electric power is supplied from the control device 20X to the magnetic bearing main unit 10X via the dedicated cable 30X.
The inventors proposed a structure that a controlling section with a displacement detection sensor was mounted in a magnetic bearing main unit of a magnetic bearing device having a constitution in which such a magnetic bearing main unit and a control device were connected via a dedicated cable in order to transmit a displacement sensing signal to the control device via the dedicated cable, to control a drive circuit of an electromagnet for magnetic bearing via a compensating circuit, and to supply a driving electric power to the magnetic bearing main unit via the dedicated cable again. As a result, it has been made possible that a variation in individual magnetic bearing main unit is taken no account in design because of an adjustment by the controlling section. In addition, the magnetic bearing main unit and the control device are freely combined. The cost reduction of the entire system has been thus achieved. (See Patent Document 1.)
When a magnetic bearing main unit connected with a high-speed rotational body such as a turbo-molecular pump and a control device are combined, because a compensating characteristic necessary for a magnetic bearing control varies according to a structural difference of a pump side, some model identification methods of a magnetic bearing main unit have been proposed to prevent an occurrence of an abnormal control caused by a mistake of a combination. For instance, proposed methods include a method for identifying a model with the specificity of a characteristic by providing a specific element such as a resistor and an inductors to the inside of a pump, a method for identifying the specificity of a model by detecting an electric characteristic of a motor mounted to a pump, a method for identifying the specificity of a model by measuring a control characteristic of a magnetic bearing, and a method for identifying a model by mounting a mechanism for storing control characteristic data on a pump and reading the data at a start of a power supply.
FIG. 26 shows a block diagram of a magnetic bearing device 100Y for executing a conventional model identification. In FIG. 26, the magnetic bearing device 100Y includes a magnetic bearing main unit 10Y, a control device 20Y, and a dedicated cable 30Y for the connection. The magnetic bearing main unit 10Y has the electromagnet 51 for magnetic bearing as well as the positional displacement detection sensor 52, a temperature sensor 57, a rotation sensor 58, and a motor driving coil 59. The electromagnet 51 for magnetic bearing and the positional displacement detection sensor 52 function as those of the magnetic bearing control device 100X in FIG. 25. The temperature sensor 57 detects a temperature at a predefined position of the magnetic bearing main unit 10Y provided with a heater such as a turbo-molecular pump. On the other hand, the rotation sensor 58 detects the rotational speed of a rotational shaft (11R in FIG. 1) of a magnetic rotational body (11 in FIG. 1). The motor driving coil 59 is the coil for driving a motor 14, typically supplies a three-phase alternating current to three stators constituting the motor 14, and rotatably drives a magnetic rotating body 11 extended to a rotor 15. The control device 20Y has a compensating circuit 54, a bearing drive power amplifier 55, a circuit drive power supply 56, an inverter 61 for motor drive, and a multiple signal processing circuit 62. The compensating circuit 54, the bearing drive power amplifier 55, and the circuit drive power supply 56 function as those of the magnetic bearing device 100X in FIG. 25. The inverter 61 for motor drive supplies a three-phase alternating electric power to the motor driving coil 59. The multiple signal processing circuit 62 converts the rotational speed and the temperature detected by the rotation sensor 58 and the temperature sensor 57 into a signal easily processed by the inverter 61 for motor drive and a temperature control device (not shown). A signal processing circuit such as a positional displacement detection sensor section, a temperature sensor section, and a rotation sensor section may be connected with the detection signal of the positional displacement detection sensor 52, the temperature sensor 57, and the rotation sensor 58 in order to transmit a processed signal to a control device 20.
A rotating mechanism for supporting a rotating body such as a turbo molecule pump with a magnetic bearing needs an electric control compensating circuit corresponding to a property characteristic of the rotating body for executing a magnetic levitation support control of the rotating body in a predefined position. In addition, as for an inverter for driving a driving motor for rotatably driving the rotating body, an inverter having an output characteristic corresponding to the characteristic of the driving motor is necessary.
FIG. 27 is a view showing an example of a constitution of a rotating mechanism to which a control device is connected via a dedicated cable dedicated to a magnetic bearing main unit (a rotating machinery main unit) of a turbo-molecular pump as an example of a conventional rotating mechanism. The turbo-molecular pump as a rotating mechanism has a magnetic bearing main unit 10Z and a magnetic rotating body 11Z. In the magnetic rotating body 11Z, radial magnetic bearing targets 16A and 16B, radial displacement detection sensor targets 17A and 17B, an axial magnetic bearing target 16C, and the rotor 15 are fixed around a rotational shaft 11R. The constitution includes the radial magnetic bearing targets 16A and 16B, the radial displacement detection sensor targets 17A and 17B, the axial magnetic bearing target 16C, and the rotor 15. The magnetic bearing main unit 10Z is constituted with radial magnetic bearings 12A and 12B (constituted with a radial electromagnet) facing the radial magnetic bearing targets 16A and 16B, an axial magnetic bearing 13 (constituted with axial electromagnets) facing the axial magnetic bearing target 16C, and a stator of a motor 14 for driving a rotating body facing the rotor 15. The magnetic bearing main unit 10Z executes a magnetic levitation support control (a five-shaft control) for the magnetic rotating body 11Z. A rotor blade of the turbo-molecular pump (not shown) is mounted on top of the rotational shaft.
The stator faces the outer circumference of the rotor 15. As a driving current is supplied to the stator, the rotor 15 rotates, and the rotating body 11Z rotates around the rotational shaft 11R. Radial displacement sensors 18A and 18B face the radial displacement detection sensor targets 17A and 17B and detects a displacement of the radial displacement detection sensor targets 17A and 17B in the radial direction. An axial displacement detection sensor 18C faces the lower end of the rotational shaft 11R and detects the displacement of the rotational shaft 11R in the axial direction. A casing 121 of the magnetic bearing main unit 10Z is provided with a plug-in receptacle 122 with which a plug 131 mounted on one end of a dedicated cable 30Z is connected. The casing of a control device 20Z is provided with a plug-in receptacle 141 with which a plug 132 mounted on the other end of the dedicated cable 30Z is connected. The control device 20Z can be connected with the magnetic bearing main unit 10Z via the dedicated cable 30Z.
FIG. 28 is a block diagram showing a circuit constitution of the magnetic bearing main unit 10Z and the control device 20Z. The parts indicated with the same reference numerals and symbols as in FIG. 26 are the same as or similar to corresponding parts. The magnetic bearing main unit 10Z has a positional displacement detection sensor section 52A, a temperature sensor section 57A, a rotation sensor section 58A, the electromagnet 51 for magnetic bearing, and the motor driving coil 59. The control device 20Z has a compensating circuit 54A, a multiple signal processing circuit 62A, the bearing drive power amplifier 55, the inverter 61 for motor drive, and the circuit drive power supply 56.
A position displacement sensor section 52A of the magnetic bearing main unit 10Z includes the radial displacement sensors 18A and 18B and the axial displacement detection sensor 18C. The position displacement sensor section 52A is a circuit section for amplifying the output signals of the displacement sensors by a preamplifier or the like and processing the output signals into signals appropriate for transmitting to the compensating circuit 54A of the control device 20Z. A temperature sensor section 57A of the magnetic bearing main unit 10Z includes a temperature sensor 57 provided to a predefined position of the magnetic bearing main unit 10Z. The temperature sensor section 57A is a circuit section for amplifying the output signal of the temperature sensor 57 by a preamplifier or the like and processing the output signals into a signal appropriate for transmitting to the multiple signal processing circuit 62A of the control device 20Z. A rotation sensor section 58A includes the rotation sensor 58 for detecting the rotational speed of the rotating body 11Z. The rotation sensor section 58A is a circuit section for processing the output signal of the rotation sensor 58 into a signal appropriate for transmitting to the multiple signal generation circuit 62A of the control device 20Z. The electromagnet 51 for magnetic bearing of the magnetic bearing main unit 10Z is constituted with the radial magnetic bearings 12A and 12B and the axial magnetic bearing 13. The motor driving coil 59 is a coil of the rotating body drive motor 14 as a stator. The compensating circuit 54A and the multiple signal processing circuit 62A are different from the compensating circuit 54 and the multiple signal processing circuit 62 in FIG. 26 only in that a processed signal is received.
The compensating circuit 54A of the control device 20Z has a function as a control signal generating circuit. The compensating circuit 54A receives the output signals from the radial displacement sensors 18A and 18B and the axial displacement detection sensor 18C of the position displacement sensor section 52A and generates a control signal for controlling the radial magnetic bearings 12A and 12B and the axial magnetic bearing 13. The control signal generated in the compensating circuit 54A is output to the bearing drive power amplifier 55, is amplified by the bearing drive power amplifier 55, becomes a control current, and supplied to the electromagnet 51 for magnetic bearing, which includes the radial magnetic bearings 12A and 12B (the radial electromagnets) and the axial magnetic bearing 13 (the axial electromagnets). As a result, the rotating body 11Z is levitationally supported by a magnetic force generated by the radial electromagnets 12A and 12B and the axial electromagnet 13. In addition, a driving current is supplied to the stator of a motor 14 for driving the rotating body 11 from the inverter 61 for motor drive, and the rotating body 11 rotates around the rotational shaft 11R.
Recently, a control device used for a turbo-molecular pump in which a rotating body is supported by a magnetic bearing is not often individually prepared as a dedicated control device corresponding to a model of a turbo-molecular pump but often prepared as an integrated control device covering a predefined range of specifications in consideration of a balance between production cost and the number of products. Such a control device is often used by changing an internal setting (adjustment). In other words, it is preferable to drive a plurality of models of the turbo-molecular pumps by an identical control device in relation to an electric circuit design from a technical viewpoint and from a viewpoint of cost.
However, there are problems described below. As an internal setting of a constitutionally identical control device is incorrect, a turbo-molecular pump cannot be normally driven. When a control device at a site of use needs to be used for a turbo-molecular pump corresponding to a different setting from the original, the control device has to be returned inconveniently to its manufacturer for the change of the internal setting. Because of failures of a control device integration, cost reduction does not advance.
As a counter measure, it is considerable that a control device is provided with a setting function of a turbo-molecular pump to be connected for making a setting according to the model of the turbo-molecular pump when a connection is made. However, because a setting distance between a control device and a pump is long or because a wiring in a device is complex in the case of a turbo-molecular pump or the like, it is not possible to discriminate which turbo-molecular pump is connected with the control device in a use condition, so that the aforementioned conventional device is not practicable. As a result, a function for a control device to identifying a model of a connected turbo-molecular pump has been wanted as a function of a control device.
On the other hand, a magnetic bearing mechanism for supporting a rotating body by a magnetic levitation is so designed that the installing orientation of the rotating body is free in consideration of its function. However, it is understood that a stable control is executed when a magnetic bearing control characteristic for use is changed on the basis of a difference in the installing orientation of the whole turbo-molecular pump according to the weight of the rotating body and the constituent features of the magnetic bearing in consideration of practicality.
The conventional methods described below have been proposed for an identification of a model of a turbo-molecular pump main unit. According to a method, a model identification element of a resistor or the like provided in a pump main unit is determined by a signal means sent from a high hierarchy control device, and the compatibility between a turbo-molecular pump and a control device is established. According to a method, a magnetic property of a motor coil is detected on the side of a control device in order to detect a property of the turbo-molecular pump, and the compatibility between a turbo-molecular pump and a control device is established. According to a method, a DSP (Digital Signal Processor) is used for mechanically moving and vibrating a rotating body, and the model of the turbo-molecular pump is identified on the basis of the property data on the turbo-molecular pump obtained through the response. (See Patent Documents 2 to 11)
[Patent Document 1] JP-A (Patent Laid Open)-2001-352114
[Patent Document 2] JP-Patent-3382627
[Patent Document 3] JP-Patent-3457353
[Patent Document 4] JP-A-H10-77993
[Patent Document 5] JP-A-H10-122182
[Patent Document 6] JP-A-H11-294454
[Patent Document 7] JP-A-H11-311249
[Patent Document 8] JP-U (Utility Model Laid Open)-H04-46226
[Patent Document 9] JP-U-H04-62393
[Patent Document 10] JP-A-H04-42290
[Patent Document 11] JP-A-2003-148386